The present invention relates to methods and apparatus for allocating bandwidth among the nodes of a Resilient Packet Ring (RPR) network.
Rings are the most prevalent metro technologies because of their protection and fault tolerance properties, but the current metropolitan ring networking technologies exhibit several limitations. In a SONET ring, each node is granted with the minimum fair share, but it is not possible to reclaim the unused bandwidth; moreover, 50% of the potentially available bandwidth is reserved for protection, thus resulting in poor utilization. On the other hand, a Gigabit Ethernet ring assures full statistical multiplexing at the expense of fairness. The RPR is used to mitigate the respective underutilization and unfairness problems associated with the current SONET and Ethernet technologies.
The RPR is defined under IEEE 802.17 and has been proposed as a high-speed backbone technology for metropolitan area networks. The key performance objectives of RPR are to achieve high bandwidth utilization, optimum spatial reuse on the dual rings, and fairness. The challenge has been to design an algorithm that can react dynamically to the traffic flows in achieving these objectives. The RPR fairness algorithm is comparatively simple, but it has some limitations that have heretofore been unsolved. One of these problems is that the amount of bandwidth allocated by the algorithm oscillates severely under unbalanced traffic scenarios. These oscillations represent a barrier to achieving spatial reuse and high bandwidth utilization.
DVSR was another algorithm proposed to solve the fairness issue with no oscillation at the steady state, but at the expense of a high computational complexity O(NlogN), where N is the number of nodes in the ring.
The conventional SONET, Ethernet, and RPR technologies do not balance the competing underutilization and unfairness problems as well as addressing cost and complexity issues. Accordingly, there is a need in the art for a new approach to allocating bandwidth in a resilient packet ring environment.